Window Sill Repair

Rotten Window Sill Repair
Rotten window sill
repair & replacement

Wooden Window Sill Repair & Replacement

Window sill repair is one of our most common call-outs. Often bearing the brunt of the British weather, sash window sills need an experienced hand to repair properly. The external window sill is one of the main sections of timber to deteriorate as, dependent on the elevation, decoration regime, and whether the window is operational, the sill can absorb rainwater which leads to rot setting in. But this can be easily combated if they are maintained properly. Where the sill is too rotten to be economically repaired we craft a new sill from Sapele Hardwood profiling it to match the existing style.

Why Choose Ventrolla for your Window Sill Repair and Replacement?

Our method of repairing and replacing rotten wooden window sills ensures the entire box frame retains its strength and structural integrity. Our installers have replaced or repaired thousands of window sills and take pride in their work.

Rotten Window Sill Repair
Wooden Sash Window Sill Replacement
Wooden Sash Window Sill Replacement
Wooden Sash Window Sill Replacement
Wooden Sash Bay Window Sill Replacement
Wooden Sash Bay Window Sill Replacement
Wooden Sash Bay Window Sill Replacement

It is often misunderstood that the north-facing windows would be the worst affected because of the lack of sun. In fact the opposite is true; generally, it is the south-facing windows where early deterioration occurs due to sunlight cracking the paint, allowing moisture to penetrate the sill.

The Ventrolla free, no-obligation survey carried out produces a window condition report which identifies whether a sill repair or replacement is required.

Dependant upon the location and amount of rot, sills can be repaired by removing the rotten timber and using Ventrolla’s special wood stabiliser and unique two-part epoxy resin; the Ventrolla VR90 Wood Repair System.


Should a repair not be possible due to the location or extent of the rot then a replacement sill is advised along with the outer lower box section (usually up to 300mm up the frame). This ensures that any rot in the outer cheeks or pulley stiles is also removed.


The new replacement sills are manufactured from the finest timber and profiled to match your existing window sill. The choice of timber will depend upon preference and budget. Your Surveyor will be on hand to advise you of the options available.


Replacing the complete sill and outer lower box assembly ensures any rot is removed completely and that new, well-sealed joints are constructed. This guarantees the box frame retains its strength and integrity, and that no gaps are left between the sill and the frame, thus preventing water ingress. Any exposed timber is then primed ready for painting by others.

"Our experience with Ventrolla, from start to finish, has been outstanding. The windows look superb and absolutely deliver what was promised in terms of performance. The installation was very efficient, neat and done with the utmost professionalism and engagement. Well done, guys, and thanks."

Peace of mind

Enjoy easy future maintenance of your replacement or new double-glazed windows, that not only come with a 5-year guarantee but can also withstand 71 mph winds! All our complete new double-glazed windows come with a FENSA certificate for that extra peace of mind. Visit our ‘contact us’ now page and let us help you make your windows exceptional.